FIG. 1 shows a fuel injector known from the related art, having a conventional three-part design of an internal metallic flow guide part and a housing component. This internal valve tube is formed by an inlet connecting piece forming an internal pole, a non-magnetic intermediate part and a valve seat carrier accommodating a valve seat. An axially movable valve needle situated in the valve seat carrier includes an armature and a spherical valve closing body as well as a connecting tube that connects the armature to the valve closing body. The three individual components of the valve needle are fixedly joined together by an integral joining method, welding in particular.
German patent document DE 40 08 675 A1 discusses such an electromagnetically operatable valve in the form of a fuel injector. The internal valve tube forms the basic skeleton of the entire injector and has an essential supporting function in its entirety for the three individual components. The non-magnetic intermediate part is fixedly and tightly connected to both the inlet connecting piece and to the valve seat carrier by welds. The windings of a solenoid are inserted into a plastic coil carrier, which in turn surrounds in the circumferential direction a part of the inlet connecting piece used as an internal pole and also surrounds the intermediate part. An axially movable valve needle situated in the valve seat carrier includes a sleeve-shaped armature and a spherical valve closing body as well as a connecting tube that connects the armature to the valve closing body. The connecting tube is fixedly attached by welds to both the armature and to the valve closing body.
German patent document DE 195 03 224 A1 discusses another electromagnetically operatable valve in the form of a fuel injector. The fuel injector has a spherical valve closing body cooperating with a valve seat, the valve closing body being mounted on a closing body carrier in the form of a plastic tube, while an armature is attached to the plastic tube at the end opposite the valve closing body. These components together form an axially movable valve needle. The lower end of the plastic tube is designed in the shape of a spherical cap and the valve closing body is positively secured in the convex recess with the aid of a snap-on connection. The plastic tube has a spring-elastic design in the area of the lower recess because holding jaws must enclose the valve closing body. In order to ensure that the spherical valve closing body is firmly secured, the holding jaws enclose the valve closing body over its equator, so that the opening diameter of the recess on the plastic tube below the equator of the valve closing body is smaller than the diameter of the valve closing body.